Rotating chair arm structure



April 18, 1961 F. w. BECHTOLD ROTATING CHAIR ARM STRUCTURE 3 Shets-Sheet 1 Filed Jan. 29, 1960 INVEN TOR. FQIEDRJCH W. BEc HTo LD M 9%,DZZ, v- :42:42,

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ROTATING CHAIR ARM STRUCTURE Filed Jan. 29, 1960 5 Sheets-Sheet 2 INVENTOR. T IZlEDQJCH W. BECHTOLD BY p v SEN-m2 ATTORNEYS April 18, 1961 F. w. BECHTOLD ROTATING CHAIR ARM STRUCTURE 3 Sheets-Sheet 3 Filed Jan. 29, 1960 5 w illwmmz gf INVENTOR. .F'meozzncu W. BEcHTo LD z ka aa AT TORM EYS United States Patent norxrmo CHAIR ARM STRUCTURE Friedrich W. Bechtold, West New Brighton, N.Y., as-

signor to The S. S. White Dental Manufacturing Cornpany, Philadelphia, Pa., a corporation of Pennsylvania Filed Jan. 29, 1960, Ser. No. 5,466

11 Claims. (Cl. 155198) This invention relates to adjustable arms for chairs, for example the chairs employed by dentists for seating patients, and is particularly concerned with pivoting and locking structures therefor.

Such employment of arms which can be moved apart is in itself known. In the present invention, the arm can be smoothly formed and blended smoothly with the chair frame, and is competent of rocking through a large angle of motion and accurate and sturdy locking at any desired position.

An object of the present invention is the provision of a chair assembly with an adjustable arm structure located concentrically with the axis of motion, and having a control means positioned on a relatively fixed part of the chair assembly.

Another object is the provision of such an assembly in which the arm is easily removable with pivotal and locking structures for inspection, repair and replacement.

Another object is the provision of such an assembly in which interengaging parts are provided on the relatively fixed structure and on the movable arm, the parts being movable along the axis for locking the arm, and with a control means accessible on the relatively fixed structure for moving the said interengaging parts axially.

With these and other objects in view, as will appear in the course of the following description and claims, an illustrative embodiment of the invention is shown in the accompanying drawings, in which:

Fig. 1 is a side view of a chair assembly including two of the movable arms;

Fig. -2 is a front view, indicating adjusted positions of the arms;

Fig. 3 is an axial section on an enlarged scale, taken substantially on the line 33 of Fig. 2;

Fig. 4 is a radial section, substantially on of Fig. 3, at a larger scale;

Fig. 5 is a fragmentary section, on a greatly enlarged scale, substantially on line 55 of Fig. 4;

Fig. 6 is a radial section, substantially on of Fig. 3, at a larger scale;

Fig. 7 is a radial section, substantially on line 7-7 of Fig. 3, at a larger scale;

Fig. 8 is a radial section, substantially on line 8-8 of Fig. 3, at a larger scale.

In these drawings, the illustrated chair is for dentists use; and has a base 10 for mounting on a floor, with a telescoping column 11 rising therefrom and having at the top a seat structure 13 with a foot rest 15. A tilting back 16 is pivoted relative to the seat structure 13 for adjustment to and locking in various positions by devices not further shown, and which may be of forms known in the art: and a head rest 18.

The seat structure 13 includes lateral portions 20 which are hollow with a bore 23, as shown in Fig. '3; and may be formed as castings around a sleeve 24 which provides the bore. The arm rests proper 21 are connected with a portion 22 extending radially from the axis of the bore 23 in the respective fixed portion 20.

line 4 4 line 6-6 Patented Apr. 18, 1961 ice A pivot shaft 25 is closely received in the inner end 23a of the bore 23 at its reduced cylindrical portion 26, and has opposed flats 27 on a larger portion and within the outer part of the bore 23. The end of the larger portion extends into the arm portion 22 and has a longitudinal slot 28 which is broadened at the bottom to provide walls 29 which converge from the lower side toward the upper in Fig. 6. A wedge block 30 fits these 'walls, and screws 31 in the arm portion 22 can be rotated to force the block 30 into the shaft slot 28 and against the walls 29 for forcing the parts of the shaft radially into tight holding engagement with the inner wall surfaces 31 of the arm portion 22.

A first plurality of friction washers 35, Figs. 3 and 8, each have circular outer edges so that they can be moved into the bore 23, and have chordal inner edges 36 for close engagement upon the flats 27, whereby these washers are caused to rotate with the shaft 25. A second plurality of friction washers 40, Figs. 3 and 7, have projections 41 at their outer edges, for engaging in the spline grooves 42 inside the lateral portion 20, and are circular at their inner edges for a sliding and rotating fit on the larger portion of the shaft 25. The washers 35, 40 are arranged alternately on the shaft 25, with friction washers 44 interposed between them, these intermediate friction washers having circular inner and outer edges.

A collar assembly 45 is secured to the shaft 25 by a diametrical pin 46 so that it is fixed against axial or rotative movement relative thereto. The washer assembly abuts against the collar assembly 45, with a washer 35 in contact therewith. A ram ring 47 fits over the larger portion of the shaft 25 and can be pressed axially along the shaft; with abutment against the end washer 40 of the washer assembly. A ball race 43 abuts against the ring 47, and has its opposite face grooved to receive the balls 49 carried in an annular retainer 50. An annular locking cam 51 is slidable along the reduced portion 26 of the shaft and has depressions 52, Figs. 4 and 5, in one face, equal in number to the number of balls 49 and cooperative therewith to press these balls and therewith the ram ring 47 toward the washer assembly upon rotation of cam 51 in one direction. A second retainer 53 has balls 54 therein, for like cooperation with a set of depressions 52 in the other face of the cam 51. These balls '54 engage in a groove in the face of the ball race '56. An actuating rod 60 is threaded into the cam 51 and extends-through a slot 61 in the respective lateral portion 20 for access, so that upon moving the rod 60 along the slot, the cam 51 is rotated about the shaft axis. The rod 60 may have a T-shaped outer end for easy operation.

The washer assembly, ram ring, retainers, cam and ball races can be assembled upon the shaft 25, and then introduced into the bore 22 in the respective portion 20, rotating each washer 40 as necessary to aline its projections 41 with the spline grooves in the portion 20. When fully introduced, the free end of the reduced portion 26 of the shaft is rotatably received in a bearing 63 at the bottom of the bore 22 and with the ball race 56 in abutment with a wall surface 64 around the bearing 63.

An externally threaded clamp ring 65 can rotate about the larger portion of the shaft 25 and be engaged with threads inside the bore 22 at the outer end thereof. This ring is rotated to advance it into the bore 22 until the assembly is completed, with partial rotation of the shaft 25 if necessary to assure that the balls 50, 54 are seated in respective depressions 52. The actuating rod 60 is introduced through its slot and threaded into the cam 51; and moved to locking position, that is, the position at which the ram 47 has been moved to greatest separation from the ball race 56. The ring 65 is then rotated until a desired torque, e.g. 100 foot-pounds, is required to rotate the shaft 25 in the extension 20 and is held by a screw 66. The movable arm assembly 21, 22, with the locking wedge 30 held loosely by the screws 31 is then slid over the protruding end of the shaft 25; and the screws 31 rotated to tighten the shaftwithin the portion 22. The movable arm is now held in this position. The portion 22 may be reduced to a smaller diameter 68 at its end, to fit inside the bore 23; and a sealing and decorative ring 69 may be included between the parts.

It is preferred, Fig. 5, to form each depression 52 with a deeper end 70 ending at a wall 71 which prevents further relative travel of the respective ball 49 or 54; a rising slope surface 72 having a minor dip 73 adjacent the shallower end of the depression 52; and an end wall 74 for limiting the ball motion. With such arrangement, with each ball at the deepest part of 70 of its depression, there is no end thrust upon the washer assembly, and the arm 21 is free to move; as the cam 51 moves and the ball travel relatively to the right in Fig. 5, end thrust develops. At proper adjustment, the inherent elasticity of parts permits the ball to come to the position 75, in the clip '73 while exerting its part of the endwise thrust; and therewith is held against accidental return toward the deeper part 70 of the depression.

If the arm position is to be changed, the actuating rod 60 is moved along its slot, so that the cam 51 is rotated, and the deeper parts of depression 52 are presented to the balls 5!}, 54 and therewith the axial clamping effort upon the ram ring 47 is reduced. The arm can now be rocked to a desired position. The actuating rod 60 is moved back, so that the cam 51 now presents the shallower parts of its depressions 52 to the balls, and an axial clamping force is exerted upon the ram ring 47, and therewith the washer assembly is pressed tightly together, with frictional resistance to relative rotation of the pluralities of washers 35, 40 being present between each two adjacent washers, and the total frictional effort being effective to prevent movement of the chair arm.

As the cam 51 rotates, the balls 50, 54 roll along the surfaces of the depressions 52. and likewise travel along the surfaces of ball races 48, 56 so that small effort upon the actuator rod 60 is required to attain a strong locking.

The parts may be removed for inspection and repair by loosening the screws 31 and removing the arm assembly 21, 22; and then backing out of the clamp ring 65 until free of the threaded part of the bore in extension 20. The actuating rod 60 is removed. The shaft 25, 26 and the locking parts can then be withdrawn.

The illustrative embodiment is not restrictive; and the invention can be employed in many ways within the scope of the appended claims.

What is claimed is:

1. A chair assembly including a seat structure and an arm support; said seat structure including an extension at a side thereof with a bore therein, a shaft secured to the arm support and extending into said bore, a first plurality of friction washers on the shaft and conformed to engage the shaft and rotate therewith, a second plurality of friction washers positioned alternately with washers of the first plurality and fitting within the bore and conformed to be held by the extension against relative movement about the shaft axis, means for detaining the shaft in said bore, and means for pressing the Washers together for controlling the movement of the arm support relative to said seat structure.

2. A chair assembly as in claim 1, in which the detaining means includes a collar fixed on the shaft, against which the axial thrust of the Washers is received, and a clamping ring received in the bore and secured to the said extension, said clamping ring being efiective to support the collar under said axial thrust and to hold the shaft in the bore.

3. A chair assembly as in claim 2, in which the clamp ing ring is threadably engaged in the Wall of said bore whereby the axial thrust of said washers may be regulated.

4. A chair assembly as in claim 1, in which the pressing means includes a cam rotatable about the axis of the shaft, a cam actuator connected to the cam and projecting for manual access outside said extension.

5. A chair assembly as in claim 4, in which thrust members are positioned on the shaft at the ends of the cam, one said thrust member being engageable with said bore and the other said thrust member being effective to deliver an axial thrust against the washers, said cam having depressions at its ends, said depressions having higher and lower portions, and rotatable elements between said depression portions and said thrust members.

6. A chair assembly as in claim 5, in which the cam has several depressions in each end, and the rotatable elements are balls.

7. A chair assembly as in claim 4, in which the shaft has a larger and a smaller diameter, the smaller diameter being engaged in a hearing at the bottom of the bore, and the larger diameter having a part of its surface conformed for receiving the Washers of said first plurality, said shaft part being located within the bore, and said cam being located for rotation about the smaller diameter of the shaft.

8. A chair assembly as in claim 1, in which the shaft has an axial slot at a part thereof located within the arm support, a Wedge is carried by the arm support for engaging in said slot, and means for forcing the wedge radially relative to the slot for expanding the shaft and engaging the same with the arm support against relative rotation.

9. A chair assembly as in claim 2, in which the shaft has a flat along a part of its length, said part being within the bore, and said collar is fixed on the shaft at the end of the fiat closer to the shaft end which receives the arm support, and the Washers of the first plurality have a chordal inner edge portion to fit the flat.

10. A chair assembly including a seat structure and an arm support; said seat structure including an extension at a side thereof, with a bore therein, said arm support having an alined bore; a shaft having a larger and a smaller diameter, part of the larger diameter being within the arm support bore and another part being within the extension bore, means for fixing said shaft to the arm support, a collar around the larger diameter of the shaft and within the extension bore, a pin through the collar and shaft for preventing relative motion, a first plurality of friction washers rotatable relative to the extension and located around the larger diameter of the shaft and having at their inner edges projections engaged in the shaft to prevent relative rotation, a second plurality of friction washers rotatable relative to the shaft and having at their outer edges projections engaged in the wall of the bore to prevent relative rotation, said washers of the first and second pluralities being alternately positioned along the shaft as a washer assembly, the smaller diameter of the shaft being carried by a bearing in said bore, the bore having a radial surface, around the shaft, a cam rotatable about the smaller diameter of the shaft and having depressions in its ends, said depressions having deeper and shallower portions, and end thrust-receiving member around the smaller diameter of the shaft and between the cam and said radial surface of the bore, an axial thrust member around the smaller diameter of the shaft and between the cam and the washer assembly, means for transferring axial thrust from the axial thrust member to the washer assembly and thereby pressing the washers toward said collanballs having parts located in said depressions and other parts in abutment with the end and axial thrust members, a ring threadably engaged in the bore for pressing the collar toward the cam and effective for determining the distance of said collar from said radial surface 5 and therewith controlling the friction effect between the washers upon rotation of the cam relative to the shaft, said extension having a slot in a radial plane of the shaft and located opposite the cam, and an actuating rod threadably engaged in the cam and extending through said slot for access and effective upon movement along the slot to effect rotation of the cam and produce movement of the same so that the balls move from and toward the shallower parts of the depressions, whereby when the balls move toward the said shallower parts, an axial eifort is exerted from said surface through the end thrust member, the cam, the axial thrust members and transferring means upon the washer assembly for pressing the same against 6 said collar and therewith establish a friction efiect between said washers for restricting the relative rotation of the arm support relative to said seat structure.

11. A chair assembly as in claim 10, in which friction members are positioned between successive washers of the first and second pluralities.

References Cited in the file of this patent UNITED STATES PATENTS 877,274- Weber -QJan. 21, 1908 1,654,787 Case Jan. 3, 1928 2,844,193 Lauterbach July 22, 1958 

